Tiny Microscope Fits on Your Fingertip

Researchers have developed a "microscopic microscope" - a microscope that's small enough to fit inside a cell phone yet that still delivers top-quality magnifying power.

Optofluidic microscope. .Image: Changhuei Yang, California Institute of TechnologyThe California Institute of Technology team hopes that the tiny microscope could be appealing for detecting pathogens in developing countries, as well as for being implanted in the human body as a diagnostic tool.

The device is a type of optofluidic microscope because it combines computer-chip technology with microfluidics technology, where a fluid flow is channeled at very small scales. The microscope has no lenses or other bulky optical elements, which have been a staple of microscopes ever since the first ones appeared in the 1500s. Without lenses, microscopes can be much cheaper: the researchers expect their tool can be mass-produced for about $10.

The microscope design consists of three layers: a microfluidic channel on top, then a metal coating, and then a CCD sensor, which is similar to the sensors used in digital cameras. The metal layer has lots of tiny holes (one-millionth of a meter in diameter) that correspond to the pixels on the CCD array. The microfluidic channel carries the liquid sample, such as blood or water, to be investigated.

To image the sample, the microscope is simply positioned in sunlight or another light source. As the liquid sample flows through the microfluidic channel, a few cells pass over the holes in the metal and block the sunlight from passing through to the CCD sensor below. As the researchers explain, these shadows produce images similar to those from a pinhole camera.

This imaging part of the microscope is actually much smaller than the chip it's mounted on, so that thousands of the microscopes could be incorporated onto a single chip the size of a quarter. This could allow many samples to be analyzed simultaneously, such as blood samples for malaria, water samples for giardia, and - when in vivo - the bloodstream for spreading cancer cells.

Changhuei Yang, a lead researcher, is currently discussing the possibility for mass-production with biotech companies.

The study is published in the early edition of the Proceedings of the National Academy of Sciences.